The present invention relates to the art of pneumatically actuated telescoping masts for supporting a light or the like, and more particularly, to improvements in the connections between adjacent telescoping sections and the displacement of an internally coiled conductor for supplying power to the light.
Featherstone, U.S. Pat. No. 4,413,451; Hulse U.S. Pat. No. 6,290,377; and Hulse, et al. U.S. Pat. No. 5,743,635 are incorporated by reference for background information relating to pneumatically actuated telescoping masts of the character to which the invention is directed.
Pneumatically actuated telescoping masts are well known in the art, and are, for example, mounted on the roof of a motor vehicle such as an emergency vehicle or utility vehicle. Alternatively, mounting configurations may also involve the floor of a vehicle, allowing the telescoping mast to extend through the roof of the vehicle. The mast is generally used for positioning electrical devices, such as lighting fixtures, at an elevated point above the vehicle. The effect of a lighting fixture is to light a large area around the vehicle, allowing emergency procedures to be conducted under the light, such as at accident scenes or by utility work crews during power outages, for example. Pneumatically actuated telescoping masts are particularly advantageous for such uses, because they are lightweight, compact in the retracted position, and quickly transportable to a site by the vehicles on which they are mounted. Pneumatically actuated telescoping masts are extended and retracted using air under pressure and, in a fully extended use position, are usually vertical, although they can be inclined in the use position. The vehicle on which the telescoping mast is mounted typically includes a compressor and appropriate pneumatic controls for displacing the mast sections between retracted and extended positions. The connections between adjacent telescoping sections of pneumatically actuated masts heretofore available have been difficult and time consuming to assemble. In part in this respect, certain parts of the connections are either welded or secured with numerous threaded fasteners, whereby the resulting mast is undesirably expensive to manufacture.
Pneumatically actuated telescoping masts include power and signal cables which extend to the payload on top of the mast. A common option in this respect is to coil the cables exteriorly about and along the mast. This approach has the virtue of accessibility and flexibility but the liabilities of exposure to physical damage and to the elements. Another option is routing a coiled cable interiorly of the mast. A problem encountered with internally routed power cables is that the coiled wire forms a weak spring. With any extended length of a coil greater than about 15 feet, the coil convolutions tend to collapse in the bottom of the mast due to the accumulated weight of the convolutions. This can result in tangling and/or snagging of the convolutions with one another when the extension moves beyond 15 feet. Also, with longer, heavier wire coils, the upper end of the cable which must support the weight of the coil therebelow is stressed by the accumulated weight of the convolutions. This can lead to breakage of the cable and requires a special connection at the cable end to preclude or minimize the likelihood of such breakage.
In accordance with the present invention, a pneumatically telescoping mast is provided which minimizes or overcomes the disadvantages of prior art pneumatically telescoping masts. In this respect, a telescoping mast according to the invention is comprised of component parts by which assembly of the mast is simplified, the weight of the mast is reduced and manufacturing of the mast is more economical than heretofore possible. These attributes are achieved through the provision of improved parts and structures between adjacent mast sections. The connecting components between adjacent mast sections include parts constructed of plastic, thereby minimizing weight of the mast assembly. Additionally, the attachment of collars to the tube of each mast section is simplified so as to avoid the use of numerous threaded fasteners, thereby simplifying assembly. Each of the mast sections includes an improved arrangement for halting movement of the sections when the mast assembly is fully extended.
In accordance with another aspect of the invention, a support arrangement is provided for an internal coiled power cable which advantageously reduces the stress on the terminal upper end of the cable and reduces the tendency of a long coil to collapse and the convolutions thereof to tangle, and/or snag during extension and retraction of the mast.
It is accordingly an outstanding object of the present invention to provide a pneumatically actuated telescoping mast with an improved connecting structure between adjacent mast sections.
A further object of the invention is to provide a mast of the foregoing character with an improved connecting structure that simplifies assembly of the mast.
Still a further object of the invention is to provide a mast of the foregoing character with an improved structure for halting movement of the mast sections when the mast assembly is filly extended.
Yet another object of the present invention is to provide a mast of the foregoing character with an internal support arrangement for a coiled, internal power cable which reduces the stress on the terminal end of the cable at the top of the mast and supports the coiled cable in a manner which reduces the tendency of the cable to collapse, tangle, and/or snag during extension and retraction of the mast.
Another object of the invention is to provide a telescoping mast that is more economical to manufacture than similar masts heretofore available.
These and other objects of the present invention will be obvious or pointed out more filly in the following detailed description of preferred embodiments.